1. Field of the Invention
The present invention relates to techniques for patterning integrated circuits.
2. Description of the Related Art
Photolithography is a process used to transfer circuit patterns onto a semiconductor wafer. It uses light to transfer a geometric pattern from a photo mask to a light-sensitive chemical photoresist. A series of chemical treatments such as etching then either engraves the exposure pattern into material underneath the photoresist, or enables deposition of a new material in the desired pattern upon material underneath the photoresist. However, there is a continuing desire to scale down feature sizes. One potential solution is spacer double patterning lithography. In this approach, a first pattern is deposited on a substrate, spacers are formed using the first pattern, the first pattern is removed and a second pattern is deposited. However, many challenges are imposed by spacer double patterning, in terms of process complexity, process control and pattern formation.